Advanced Materials Research Vols. 614-615

Abstract: It is difficult to achieve precise fault location for hybrid transmission line of distribution network, because it has wave impedance discontinuity point. Section location is the premises of precise location. On the basis of others’ research results, the matrix algorithm of distribution network single-phase ground fault section location is improved in the paper. It makes the sparse degree of matrix is higher, computation is less. An algorithm of recovery the network topology only based on the fault description matrix is suggested when the visualization data of a line network topology is loss or the operating is in the non-visual condition. The method is applied to revise fault description matrix, so that the matrix algorithm has some fault-tolerance. The applicability and validity of the improved algorithm was verified by an illustration. The method realizes the fault section location, and the subsequent accurate fault location is presented in this paper.

Abstract: In recent years, a new type of 380V low voltage fixed circuit breakers are used in newly built substations. Fixed circuit breakers without chassis only have two states. They are on and off. They can not provide a clear break point in circuit. So Their isolation function is not obviously. Low voltage equipment in Hub substations should have automatic mutual transfer function. Recently Automatic Transfer Switch (ATS) is often chosen in the newly built digital substation, intelligent substation or large hub substations. Automatic Transfer Switch has interlocking function to avoid the collision of two different power. With the popularize of new equipment such as the 380V fixed circuit breaker and Automatic Transfer Switch, the operation and management of low-voltage equipment in substations puts forward higher requirements as well. The conclusion contains the better ways in operation and maintenance of these new low-voltage equipment.

Abstract: This paper presents the main results of a work aimed at resolving voltage sags in customer substation, by measuring and analyzing the power quality problem. The work is based on a power quality monitoring system built in the customer substation. A large number of power quality events are recorded to pick up the voltage sag performance, the voltage sag characteristics and the number of sags issummarized. SARFI-curve method according to IEEE P1546 is used to analyze the sag influence on customer’s sensitive electrical equipment. Combined with the specific situation, a set of solution to voltage sag problem is proposed to improve power conditioning for sensitive loads and reduce economy losses.

Abstract: Divide the network into several subsystems then restore the subsystems separately can accelerate the restoration procedure after a main blackout occurs. In this paper, the strategy of black-start system partitioning based on nodes voltage is proposed. The strategy considers the node voltage as partition criterion. By power flow calculating gets nodes voltage and sorts them and then select voltage threshold to partitioning the groups of the nodes according to nodes voltage and the number of black-start units. The algorithm has a rigorous theoretical basis for it based on communities finding theory of complex network. The effectiveness of the proposed method is validated by studying the IEEE 118-bus case.

Abstract: Through the furnace-flame image-signal processing for power plant, effective-temperature field proportions, high-temperature field proportions, centroid offset distances, and circular degrees in high-temperature field can be all obtained. What’s more, based on the above data and related signals collected by sensors such as flame detectors as a criterion, the Kohonen’s self-organizing neural network is introduced to distinguish the states of furnace flame. Therefore, the opening incremental adjustment is proposed to achieve real-time control of furnace flame.

Abstract: The AC-DC method (the AC method combined with the DC method) has integrated the superiority of the AC method’s easy measurement and the DC method’s reliability, so it has achieved some degree of use. The method before only took the ground resistor as the condition of combination, so it is not perfect. Based on deep analysis on the AC method’s reflect factors, this paper drew a conclusion that the reliability of the AC method is affected by the fault resistor and the line’s distributed capacitance. The paper took the impedance phase as the integration condition, using the AC method while impedance phase meets certain conditions, using the DC method on the other situation. This strategy combined the affluence of ground resistor and distributed capacitance effectively, so it can promote the application on spot of the AC-DC method.

Abstract: The effective methods of the ageing and life assessment for large and medium-sized power transformers used in nuclear power plants are analyzed and described, including the thermal ageing life assessment method for transformer solid insulation, the gas analysis method of CO and CO2 in the transformer oil, the average degree of polymerization method, furfural content analysis method, and the analysis method based on the insulation ageing-related electrical parameters. The analysis results show that the methods used can reasonably assess the remaining life of the transformers. These methods have important reference value to the ageing and life management for the large and medium-sized power transformers in nuclear power plants.

Abstract: In order to meet the requirement of high voltage transmission lines monitoring system, this paper presents a heterogeneous integrated network which contains Optical Ethernet, broadband wireless communication networks and wireless sensor networks in high voltage transmission line monitoring system. Moreover, considering the characteristics of the heterogeneous integrated communication network and analyzing the features of service security mechanism in communication network, this paper proposes an authentication and encryption security system, which has certain value in the authentication and encryption aspects to electric power system communication.

Abstract: In order to improve the stability and reliability of switch mode power supply, the mathematical model of high frequency transformer is established with considering the effects of the leakage inductance of the high frequency transformer on the working state of DC-DC full bridge converter circuit. A finite element analysis method for two dimensional transient field circuit directly coupled of transformer in the case of full bridge inverter is proposed. Transformer inductance parameters are calculated using the method of field energy, which may provides the basis for the design of switching mode power supply transformer.

Abstract: Insulated copper busbar is widely used as a new type of electrical equipment in recent years. The joint of the busbar is linked with soft connection copper belt in the field. So, it is very easily lead to the metal protrusion defect at the joint. The metal protrusion detect at joint with entity insulated copper busbar is builded in lab. The partial discharge characteristics of this defect is studied under different applied voltage and the results show that such defect has apparent polarity effect, the discharge always appears in the negative half cycle. The discharge amplitude will not be increased very much with increasing of applied voltage but the discharge frequency will be increased significantly. The results provide the basis of laboratory studies for the field testing of insulated copper busbar.